【作者】 林晓辉；

【导师】 史铁林； 廖广兰；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 作为半导体制造领域的一项新兴的使能技术,晶圆直接键合已经在越来越多的领域发挥了重要的作用。晶圆键合可以使得经过抛光的半导体晶圆在不使用粘结剂的情况下结合在一起。这种技术可以用于微电子、微机械、光电子等诸多领域。因此,深入研究晶圆键合的技术和应用的细节,对于推进晶圆键合在半导体产业中的应用具有重要的意义。本研究工作将涉及晶圆键合的技术和应用的一些方面。晶圆键合技术是其得以用于实际器件制作的基础,研究中,完成了对晶圆低温键合进行理论建模、工艺改进以及质量的评估。在晶圆键合的应用方面,将工艺运用于多层晶圆键合,带图形晶圆键合以及微流管道器件的制备。在晶圆键合的理论研究中,本文利用平板接触的力学理论,结合硅晶圆键合的实际情况,建立了一套键合模型。该模型中,晶圆的表面形貌凹凸采用更接近实际的高斯分布。通过模型,详细地分析了晶圆在接触过程中,由于弹性形变造成的弹性力以及由于表面活化造成的吸附力与晶圆距离之间的关系,清晰地解释了晶圆键合中,不同接触距离对键合力的影响。通过将仿真结论与实际键合发生的条件进行对比,提出了晶圆发生自发键合的理论判据。这一判据给出了在不同活化质量下对晶圆表面粗糙度的要求,具有相当的实用性。在晶圆键合的工艺探索中,基于将干法和湿法活化相结合的思想,采用了紫外光辅助晶圆键合的工艺流程。通过对比实验发现,合适的紫外光照射能够大大提高晶圆键合的质量,对这一现象,研究工作从化学热力学的观点出发,对比了紫外光和各种化学共价键的键能,并根据紫外光的机制,阐述了其对于晶圆表面清洗和活化的详细机理,提出了其在晶圆表面聚集羟基的流程。在晶圆键合的质量评估中,对样片进行了恒温恒湿,高低温循环以及气密性的测试,对晶圆键合进行多方面的质量检测和可靠性评估。此外,针对经过长时间的紫外光照射,键合强度降低这一现象,本研究的测试环节中利用原子力显微镜对晶圆表面的粗糙度和承载率做了进一步的测试,并给出了合理的解释。将技术探索的成果用于晶圆键合的应用研究,我们尝试制备了三层晶圆键合,获得了良好的界面特性,为制备三维互联结构打下了良好的基础。此外,进行了带图形晶圆的键合,使用经过光刻,显影,刻蚀等流程的带图形晶圆与裸晶圆进行键合,键合结果表明,使用该工艺流程可以获得良好的界面一致性,进一步确认了其对晶圆表面的清洗活化能力。最后,将多种工艺结合,制备了血细胞计数器的微流体分析芯片。通过对血细胞计数器的工作原理,组成部分的详细分析,定制了其具体的制备流程,成功地使用硅晶圆直接键合技术,实现了微流管道芯片结构层和封盖层的键合,获得了均匀的键合界面。更多还原

【Abstract】 As one of the newly-emerged enabling technologies, wafer direct bonding has been playing key roles in more and more fields. Without any kind of glue, wafer bonding technology is able to integrate two polished semiconductor wafers and thus be used widely in fields like micro-electronics micro-mechanics and opto-electronics. Researching deeply into detailed aspects of wafer bonding technologies and applications will help to promote its maturity in semiconductor industry. This research work covers some of the aspects in wafer bonding technologies and applications. As the foundation of device manufacturing, the bonding technologies introduced in this dissertation covers the aspects of theories, processes and reliability tests. For the applications, wafer bonding are applied to multi-layer wafer bonding, patterned wafer bonding and micro fluidic devices.In the research of bonding theories, starting from the basic mechanism of plate contacting theory, a set of bonding model is established according the properties of the silicon wafers. In the model, the surface topography is described to obey the Gaussian distribution. By calculating and analyzing the model in detail, the relations, in the silicon wafer direct bonding, among the elastic force due to surface deformation, the adhesive force due to surface activation and the distance due to surface separation are unveiled. The impact of separation distance on bonding force is explained in detail. By comparing the results of models and the conditions of the real bonding, a practical surface roughness criterion for spontaneous bonding, which includes the impact of surface activation quality, is proposed and proved to be in agreement with the experimental data.In the process exploration, based on the idea of combining both wet chemical activation and dry plasma activation, UV exposure is employed in wafer bonding process. Results of comparative trials show that proper UV exposure increases the bonding quality dramatically. From the view of the chemical thermodynamics, by comparing the energy between UV and chemical bonds, the mechanisms of UV cleaning and UV activation are explained in detail, as well as different ways by which hydroxyl groups are accumulated on the surfaces.In the quality tests and reliability evaluations, different aspects of bonded samples are examined by carrying out experiments of constant temperature and humidity treatment, thermal cycling treatment, as well as the air tightness evaluation. Besides, It is found that prolonging the exposure time may cause decrease in bond quality and the reason for which is explained based on the results of surface roughnesses and bear ratios from AFM measurement.Wafer bonding applications: By applying what we have explored into application of wafer bonding, triple-layer bonding is carried out and satisfying results are achieved to lay a foundation for 3D interconnected structures. Besides, the ability of this bonding process in cleaning and activating the silicon surface is confirmed again by observing uniform interfaces achieved by bonding bare silicon wafers with patterned wafers. Finally, by combining wafer bonging technology with other processes, a micro fluidic chip for hemocytometer is prepared. After analyzing the function, components and process in detail, wafer bonding is served as a packaging method to integrate the structural layer and sealing layer.更多还原